[Telepathy-commits] [telepathy-spec/master] Messages: add rationale for reversing MIME's preference order

[Simon McVittie]

---
 spec/Channel_Interface_Messages.xml |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/spec/Channel_Interface_Messages.xml b/spec/Channel_Interface_Messages.xml
index 85fdfaa..ee05c8f 100644
--- a/spec/Channel_Interface_Messages.xml
+++ b/spec/Channel_Interface_Messages.xml
@@ -297,10 +297,18 @@ USA.</p>
             display the first alternative that they understand.</p>
 
           <tp:rationale>
-            Specifying the preference order means that if the underlying
-            protocol doesn't support alternatives, the CM can safely delete
-            everything apart from the first supported alternative when sending
-            messages.
+            <p>Specifying the preference order means that if the underlying
+              protocol doesn't support alternatives, the CM can safely delete
+              everything apart from the first supported alternative when
+              sending messages.</p>
+
+            <p>The order is the reverse of MIME because MIME's rationale for
+              placing the "plainest" part first (legibility in pre-MIME UAs)
+              does not apply to us, and placing the most preferred part
+              first simplifies display (a client can iterate the message
+              in order, display the first alternative that it understands,
+              and skip displaying all subsequent parts with the same
+              "alternative" key).</p>
           </tp:rationale>
 
           <p>Clients SHOULD present all parts that are not redundant
-- 
1.5.6.5